The process for producing a bump of semiconductor device generally comprises a step of forming a thick photoresist film or photoresist pattern on such layer.
As to photoresist compositions to be used for thick photoresist film or photoresist pattern on such layer, JP2008-249993A1 mentions a positive type photoresist composition which comprises    (A) a polymer comprising 10 to 70% by mole of polymer unit derived from t-butyl(meth)acrylate and 30 to 90% by mole of polymer unit derived from a compound represented by formula (I); R1—(C═CH2)—(C═C)—O—R2, said polymer having weight average molecular weight of 50000 to 300000,    (B) an alkaline-soluble polymer, and    (C) photosensitive acid generator.